Thursday, 24 May 2012

Gemini

Project Gemini was the second human spaceflight program of the United
States of America. It operated between Projects Mercury and Apollo,
with 10 manned flights occurring in 1965 and 1966. Its objective was to
develop techniques for advanced space travel, notably those necessary
for Project Apollo, whose objective was to land men on the Moon. Gemini
missions included the first American extravehicular activity, and new
orbital maneuvers included rendezvous and docking
Gemini was originally seen as a simple extrapolation of the Mercury
program, and thus early on was called Mercury Mark II. The actual
program had little in common with Mercury and was in fact superior to
even Apollo in some ways. (See Big Gemini.) This was mainly a result of
its late start date, which allowed it to benefit from much that had been
learned during the early stages of the Apollo project (which, despite
its later launch dates, was actually begun before Gemini).
Its primary difference from Mercury was that the earlier spacecraft
had all systems other than the reentry rockets situated within the
capsule, to which access of nearly all was through the astronaut's
hatchway, while Gemini had many power, propulsion, and life support
systems in a detachable module like a huge bowl; many components in the
capsule itself were reachable each through its own small access door.
The original intention was for Gemini to land on solid ground instead of
at sea, using a paraglider rather than a parachute, and for the crew to
be seated upright controlling the forward motion of the craft before
its landing. To facilitate this, the parachute cord did not attach just
to the nose of the craft; there was an additional attachment point for
balance near the heat shield. This cord was covered by a strip of metal
between the doors. Early short-duration missions had their electrical
power supplied by batteries; later endurance missions had the first fuel
cells in manned spacecraft.
The "Gemini" designation comes from the fact that each spacecraft
held two men, as "gemini" in Latin means "twins". Gemini is also the
name of the third constellation of the Zodiac and its twin stars, Castor
and Pollux.
Unlike Mercury, which could only change its orientation in space,
the Gemini capsule could alter its orbit. It could also dock with the
Agena Target Vehicle, which had its own large rocket engine, was used to
perform large orbital changes. Gemini was the first American manned
spacecraft to include an onboard computer, the Gemini Guidance Computer,
to facilitate management and control of mission maneuvers. It was also
unlike other NASA craft in that it used ejection seats, in-flight radar
and an artificial horizon - devices borrowed from the aviation industry.
Using ejection seats to push astronauts to safety was first employed by
the Soviet Union in the Vostok craft manned by cosmonaut Yuri Gagarin.
Gemini was designed by a Canadian, Jim Chamberlin, formerly the
chief aerodynamicist on the Avro Arrow fighter interceptor program with
Avro Canada. Chamberlin joined NASA along with 25 senior Avro engineers
after cancellation of the Arrow program, and became head of the U.S.
Space Task Group's engineering division in charge of Gemini. The main
contractor was McDonnell, which had lost out on main contracts for the
Apollo Project. McDonnell sought to extend the program by proposing a
Gemini craft which could be used to fly a cislunar mission and even
achieve a manned lunar landing earlier and at less cost than Apollo, but
these proposals were rejected.
The Gemini program cost $5.4 billion dollars